A portable handheld drilling machine having an internal combustion engine is disclosed in British patent publication 2,187,664. In this drilling machine, the following components are arranged one behind the other: a transmission, a clutch, an internal combustion engine and a rear handle. An output shaft having a tool chuck extends out from the transmission. The tool chuck accommodates different tools which can be exchanged including drill bits, screw bits or the like. The transmission housing is securely attached to a machine housing wherein the engine is mounted with its cylinder, crankcase, exhaust-gas muffler and carburetor. For cooling the engine, a cooling air blower is mounted on the end of the crankshaft at the side facing away from the transmission housing. The cooling air blower supplies cooling air via a housing spiral to the machine housing. The rearward handle is attached to the rear back wall of the machine housing and serves for holding and guiding the drilling machine.
The housing is configured with spacing to the individual engine elements and is closed on all sides. Because of this housing, the engine is very large which limits its use possibilities. In addition, a drilling machine built this large is also very heavy because of the voluminous housing which affects the manipulability thereof.
It is an object of the invention to provide a portable handheld drilling machine having an adapted external housing which hardly limits the use possibilities and keeps the weight of the drilling machine very low.
The portable handheld drilling machine of the invention defines a longitudinal axis and includes: an internal combustion engine having an engine block and a crankshaft; a transmission housing accommodating a transmission therein; the transmission having an input shaft driven by the crankshaft and having an output shaft accommodating a chuck thereon; the crankshaft having an end facing away from the transmission; an engine housing for accommodating the engine therein and the engine housing having a housing spiral formed therein; a cooling air blower mounted on the end of the crankshaft for moving cooling air though the engine housing via the spiral; the engine including a cylinder, crankcase, carburetor and exhaust-gas muffler and the engine housing surrounding the cylinder, the crankcase, the carburetor and the exhaust-gas muffler; the engine housing having a handle formed thereon for holding and guiding the machine; the engine housing having a front end and a rear end in the direction of the longitudinal axis; the engine housing being open in the front and rear ends; the transmission housing being attached to the engine block; the transmission housing projecting in the direction of the longitudinal axis through the front end with a peripherally extending play (v); the housing spiral being disposed in the rear end with a peripherally extending play (u); and, the engine housing having a handle formed thereon for holding and guiding the machine and the handle extending bridge-like over the rear end of the engine housing.
The configuration of the engine housing having open ends reduces the total weight. The transmission housing is attached to the engine block. For this reason, all forces are conducted directly into the engine block. The housing itself is relieved of load and can therefore be correspondingly configured with less material. Subdividing the portable handheld drilling machine into an inner work unit and an outer housing makes possible a relative movement between the engine housing and the inner unit so that a vibration decoupling of the inner unit from the external housing is possible.
The unit, which is formed by the transmission housing and the engine, is advantageously held in the engine housing via anti-vibration elements. Preferably, such anti-vibration elements are mounted, on the one hand, on the engine and, on the other hand, on the transmission housing. In each case, two diametrically opposite lying anti-vibration elements are provided with respect to a housing partition plane. In this way, a simple assembly of the anti-vibration elements is possible. Only with the assembly of the machine housing are the anti-vibration elements placed and thereby built in. The machine housing is subdivided into two housing shells in the direction of the longitudinal axis of the drilling machine.
To achieve an advantageous performance with respect to guiding the drilling machine, the anti-vibration elements which are mounted on the transmission housing are arranged at a spacing in elevation to the anti-vibration elements provided on the engine. The anti-vibration elements of the engine are permitted to engage on the housing spiral of the cooling air blower in order to provide the largest possible spacing in the direction of the longitudinal axis of the drilling machine. In this way, all anti-vibration elements lie close to the open end faces of the machine housing.
In a preferred embodiment of the invention, an air filter housing is configured in a side wall of the machine housing. The air filter housing is preferably connected to an intake pipe ending in the machine housing. The intake pipe lies transversely to the longitudinal axis of the drilling machine and preferably extends to the opposite-lying side wall of the machine housing and is configured as one piece therewith. The intake pipe can be configured to be adapted in correspondence to the flow conditions and can especially be used as a resonance pipe in order to attenuate the intake noise. Advantageously, the inlet opening of the intake pipe lies in an intake zone to which substantially dirt-free combustion air is supplied via a vibration gap.